I just said that!

[edible_hat]

SC: I thought that ethanol was meant to give you better economy! It's come up worse.
me: It does give you better economy, it's 94 octane and the regular unleaded is 92.
SC: But it's worse than the premium.
me: That's because the premium is octane 98, higher again so you get more power per liter.
SC: No you don't, it gives you more power.

I just said that. And if you use a more powerful fuel, you get better economy. It takes a certain amount of power to move your car a certain distance, so if you get more power from the fuel you'll use less fuel.

Personally I think if he really wants more economy he should sell his Jeep Grand Cherokee and get something suited for city driving.

[JustADude]

SC: I thought that ethanol was meant to give you better economy! It's come up worse.
me: It does give you better economy, it's 94 octane and the regular unleaded is 92.
SC: But it's worse than the premium.
me: That's because the premium is octane 98, higher again so you get more power per liter.
SC: No you don't, it gives you more power.

I just said that. And if you use a more powerful fuel, you get better economy. It takes a certain amount of power to move your car a certain distance, so if you get more power from the fuel you'll use less fuel.

Personally I think if he really wants more economy he should sell his Jeep Grand Cherokee and get something suited for city driving.

Okay, , but how the hell do you convert a regular gas car into one that can use E85?
I was told the gaskets and other rubber/plastic bits on most cars designed pre-E85, and many designed after, can't handle the extended contact with the ethanol and rot out quickly. If it's not too expensive a change, I'm definitely going over, since around here E86 is like US$0.30/gal cheaper than regular gas in the area. Cheaper + higher octane = Win.

EDIT: Nevermind. I remembered our trusty pals, Google and Wikipedia, and looked it up myself. Yeah... not cheap. Great fuel if your car comes ready for E85, but the refit would require ~10,000 gallons of gas to make it break even. At my car's MPG, that's 200,000~300,000 miles. Not worth it.

[pyxee]

SC: I thought that ethanol was meant to give you better economy! It's come up worse.
me: It does give you better economy, it's 94 octane and the regular unleaded is 92.
SC: But it's worse than the premium.
me: That's because the premium is octane 98, higher again so you get more power per liter.
SC: No you don't, it gives you more power.

I just said that. And if you use a more powerful fuel, you get better economy. It takes a certain amount of power to move your car a certain distance, so if you get more power from the fuel you'll use less fuel.

Personally I think if he really wants more economy he should sell his Jeep Grand Cherokee and get something suited for city driving.

Where do you live that regular gas is 92? Here in Missouri regular is 87 I have to pay out the rear for 91 for my car, and there are only maybe 3 stores in the entire town of 200.000 that carry up to 93.

[Dave1982]

Ok, this is mostly going to be since it doesn't address SCs at all, but I'm going to put on my science hat for a bit.

me: That's because the premium is octane 98, higher again so you get more power per liter.

This is incorrect. The idea that higher octane ratings indicate a more powerful fuel is a myth. THe octane rating of gasoline is a measure of its autoignition resistance. That is, how resistant the gas is to spontaneous combustion when under pressure. Any gasoline, given enough pressure, will ignite on its own, which is actually a bad thing, because if it ignites too soon, it will have a very bad effect on engine performance. This is what is happening when an engine "knocks." The octane rating required by your engine depends on a variety of factors such as displacement, compression ratio, and aspiration (ie, normal, turbo, or supercharged). An engine with a high compression ratio or one equipped with a turbocharger may require a higher octane fuel because the higher pressure in the combustion chambers may cause "regular" gas to detonate, resulting in a knock. An engine with a knock will not produce as much power and also suffers much greater wear and tear. In fact, a bad enough detonation can ruin an engine altogether.

Interestingly, because higher octane fuels are harder to ignite, they actually produce LESS power than lower octane gas.

Where do you live that regular gas is 92? Here in Missouri regular is 87

Without getting into the technical details, there are two different types of gasoline octane ratings: Research Octane Number and Motor Octane Number. In the US and Canada, the pump octane number (sometimes known as the anti-knock index) is the average of the RON and the MON (which is why the stickers usually say (R+M)/2 method). Most of the rest of the world just goes by the RON, which is always higher than the MON. Thus, 92 octane (in Europe) is the same as 87 octane (in the US), though regular is sometimes defined as 95 RON in Europe, which would be 91 in the US.

[smileyeagle1021]

hey, us utahns are looking at missouri with envy... our regular is all the way down to 85.. though i did see one place up in Logan that offered something like 103 octane fuel.. i'll be honest... i was afraid to put it in my car.

[xcaptainhowdyx]

103 octane sounds like racing fuel, it's not legal for a street vehicle, btu strangely some gas stations have pumps for it.

[smileyeagle1021]

just out of curiousity, does anyone know what would happen if i were to put 103 octane fuel in my dinky little subcompact nissan? would it actually do anything other than a lot of my money?

[Dave1982]

just out of curiousity, does anyone know what would happen if i were to put 103 octane fuel in my dinky little subcompact nissan? would it actually do anything other than a lot of my money?

Well, I'm not an expert, so take this with a grain of salt, but my guess is nothing, so long as the fuel doesn't have more ethanol (or any other blending additive) than your engine can handle. But you are unlikely to see any benefit from a fuel higher than 87 octane (US), so yeah, it'd be a waste of money.

[edible_hat]

The idea that higher octane ratings indicate a more powerful fuel is a myth. THe octane rating of gasoline is a measure of its autoignition resistance. That is, how resistant the gas is to spontaneous combustion when under pressure. Any gasoline, given enough pressure, will ignite on its own, which is actually a bad thing, because if it ignites too soon, it will have a very bad effect on engine performance. This is what is happening when an engine "knocks." The octane rating required by your engine depends on a variety of factors such as displacement, compression ratio, and aspiration (ie, normal, turbo, or supercharged). An engine with a high compression ratio or one equipped with a turbocharger may require a higher octane fuel because the higher pressure in the combustion chambers may cause "regular" gas to detonate, resulting in a knock. An engine with a knock will not produce as much power and also suffers much greater wear and tear. In fact, a bad enough detonation can ruin an engine altogether.

Interestingly, because higher octane fuels are harder to ignite, they actually produce LESS power than lower octane gas.

In my experience, higher octane gives better fuel economy. I'm driving a 2002 Holden Barina. On regular I use 7 liters to go 100km, while on the 10% ethanol mix I use 6.5 liters. Premium is better again but not enough to justify me paying the extra premium for it.

We've got a list of which cars can handle the ethanol blend fuel, mine is on the list. Interestingly, most of the cars made after 1990 that aren't on that list are luxury cars like Bentleys and Jags.

[Dave1982]

There are a wide variety of factors when it comes to fuel economy. There may well be another characteristic of plus or premium fuel that your car does better with, just not "higher octane = more power."